1. Field of the Invention
The present invention relates to an operation circuit for use in, for example, a power switching device.
2. Description of the Related Art
Hitherto, in an operation circuit for use in an operation mechanism to drive a power switching device, as shown on page 4 and FIGS. 9 to 11 of the Japanese Patent Publication (unexamined) No. 033034/2002, two discharge switches such as thyristors are provided and controlled from outside, and turned ON in synchronization with an opening command or a closing command, and are turned OFF at the moment of completion of such opening operation or closing operation.
In the mentioned conventional operation circuit for use in an operation mechanism to drive a power-switching device of above arrangement, there exist the following problems.
In the conventional operation circuit, an opening coil and a closing coil are connected in parallel to capacitors, and electric energy is discharged by discharge switches connected in series to these two coils, respectively. In this known arrangement, the mentioned opening coil and closing coil are disposed adjacent to each other within the operation mechanism. Accordingly, a problem exists in that any induction current, which flows in a direction opposite to a current direction of the coil of the excitation side, is generated through the coil of the non-excitation side due to magnetic coupling when current is carried. Thus a magnetic flux necessary for driving is cancelled, and the generation of a driving force is inhibited.
Moreover, since the state of the magnetic coupling changes in a supersensitive manner depending on a relative positional relation between a moving element being in the stopped state and the mentioned opening coil and closing coil, another problem exists in that the operation is not stable.